Molded taper, back

A method of producing two-color pieces in thermoplastic materials by successive injection molding operations. A taper or slope in a mold that facilitates removal of the molded piece. The opposite of this is called back draft, q.v. 

Back draft (back taper, counterdraft) n. A slight undercut or tapered area in a mold tending to prevent removal of the molded part. Complete textile glossary. Celanese acetate EEC, New York, 2000. 

Nozzle designs with positive shut-off devices have been successfully used. The gas must be free to escape through the nozzle. Material freeze off in the nozzle or malfunction of the positive shut-off device could develop pressure to cause blow-back of the material through the feed zone and hopper or create hazardous conditions. In such cases, conventional free flow and reverse taper type fitted with a heater band for temperature control of the nozzle prevents nozzle drool or freeze off of the material and is used and in nylon processing. Sprue cutter is associated with the nozzle to help the process. A nozzle forms a seal between the injection system and the mold. 

Draft n A slight taper in a mold wall, proceeding inward from the parting surface to the bottom of the cavity, designed to facilitate removal of the molded object from the mold. When the taper is reversed, tending to impede removal of the article, the term back draft, or reverse draft is employed. In weaving, a pattern or plan for drawing-in. 

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